1. The Field of the Invention
The field of the invention relates to an improved powered rotary trowel for finishing environmentally resistant toppings applied over various substrates, such as concrete or wooden floors.
2. Description of the Prior Art
Various substrates, such as those made of poured concrete and the like, in many applications require a finish topping of an environmentally resistant material such as any epoxy resin and aggregate mixture. In applying such a finish, most applications are done by hand so as to ensure uniform topping thickness, film integrity as part of the topping, chemical resistance and aesthetic quality of the installation so as to keep the finish surface free of unsightly trowel marks. This exposes the worker to a substantial health hazard since close proximity to the aggregate/resin mixture during the hand troweling is required. The arduous conditions are further compounded by the need to work in a crouched or crawling position.
Attempts by workers to utilize devices and methods from the nearest related art, the use of self-propelled rotary trowels on booms for troweling concrete are quite unsatisfactory. While removing the worker from the fume area and allowing him to work upright at a reasonable speed, serious problems are created. The mass of apparatus typical for concrete troweling as taught in U.S. Pat. Nos. 2,662,454 (Dec. 1953 to Whiteman) and 4,198,178 (Apr., 1980 to Carlstrom et al (electric motors); 4,673,311 (Jun., 1987 to Whiteman) Goldblatt Tool Co., Kansas City, KS (internal combustion engine), all requiring heavy gear boxes, is about 92-250 pounds (42-110 kg). As a result, it is impossible to install a topping with a low aggregate/resin ratio, typically 5:1, as is commonly used in manual troweling since such a machine's mass will cause the trowel blades to leave unacceptable trowel marks that require repower troweling or extensive sanding after the topping has hardened. Consequently, aggregate ratios of 7 or 8:1 or higher are needed. Such ratios have diminished physical properties and aesthetic.
It should also be noted that combustion engines are not permitted to be used in food and drug manufacturing or processing sites and electric motors can cause explosions unless shielded in certain chemical atmospheres.
Further, the decorative value of these finished toppings where colored quartz is used as the aggregate cannot satisfactorily be maintained by neither heavy weight machine troweling nor by hand. This is caused by the introduction of a multiplicity of colors. Varigation creates visual problems for the manual installer since his eye cannot focus on trowel marks because of the multiplicity ofdd the colors. Further, the machine operator, as opposed to the manual artesan, cannot eliminate such marks since the quartzes included in the aggregate alter the topping composition to such an extent that a satisfactory finish is impossible. The machine trowel is no longer used for quartzes in the industry as a result.
It has been well recognized, due to the unpredictable nature of the topping setting during the installation process, that it would be useful to make the blade pitch and rotation speed variable during operation. The factors which influence this are, inter alia, aggregate/resin viscosity, ambient temperature, substrate temperature, square footage and the like. Variable pitch is taught by different means in, for example, '311 (Whiteman) above, and '980 (Morrison) above and U.S. Pat. No. 4,577,993 (Mar., 1986 to Allen, et al). It is believed that some require stopping the trowel to adjust for angle. None teaches a variable speed of rotation which is slow enough to provide a swirl free finish but rely on heavy duty gear boxes and throttles essentially to reduce the speed of the power source and regulate it to some extent. Such configurations only serve to exacerbate the problem by further increasing the mass significantly.
Prior art of interest, but which is deemed inapplicable, is USSR No. 146470 (Mar. 1961 to Kanyuka et al.) which depicts a pneumatic hand drill apparatus, useful in finishing plaster walls, to which is attached a rotary disc supporting trowel blades and a flowing water supply. Adaption of the apparent principal taught in USSR '470, rapid, wet smoothing of plaster screed or slip coats hardly would be applicable to finishing a aggregate/resin topping on a floor. Liquid flow for smoothing is desirable for plaster but not in the present application. Further, utilization and adaptation of such a device would scarcely be an improvement over hand troweling and is of too little mass to trowel a resinous topping.
It is well known in the industry that aggregate/resin mixtures of 5:1 or less will give superior toppings to the common 7-8:1 mixtures in use since the higher ratios of aggregate degrade the environmental resistance of the topping. By experimentation your inventor has found that a significant reduction in aggregate (to ratios of 5:1 and as low as 3:1) can be accomplished if the mass of the troweling device does not exceed about 40 pounds (18 kg). Further, it has been found that a mass of not less than about 20 pounds (9 kg) is necessary to maintain a useful finishing speed and a desirable finished effect.